Conventionally, a technique is known, in which an electrochemical sensor implanted, for example, in belly (abdomen) or arm of an examinee is utilized to continuously measure the numerical information in relation to a test substance contained in a body fluid, for example, the glucose concentration (so-called blood sugar level or blood glucose level) in an interstitial fluid of the examinee. The electrochemical sensor is a sensor capable of detecting a minute amount of current by utilizing the electrochemical reaction, which is suitable for the detection of a minute amount of chemical substance that causes an oxidation reduction reaction.
A biosensor, in which an enzyme is immobilized to a sensor unit to be arranged while being implanted subcutaneously beneath the skin and the enzyme reaction thereof is utilized to detect a test substance contained in a sample, is used in many cases as the electrochemical sensor for measuring the glucose concentration. Usually, the biosensor of this type has a working electrode and a counter electrode, and the enzyme (for example, glucose oxidase) is immobilized to the working electrode. A voltage is applied between the working electrode and the counter electrode, and the glucose concentration can be measured on the basis of a response current obtained thereby.
The glucose oxidase produces gluconic acid by selectively reacting on the glucose under an existence of oxygen. On this occasion, the oxygen is reduced, while hydrogen peroxide proportional to a quantity of the glucose is generated. The hydrogen peroxide can be oxidized electrochemically easily and can be therefore measured by use of a pair of electrodes. Namely, the response current value can be obtained by the electrochemically oxidizing the hydrogen peroxide generated by the enzyme reaction of the enzyme as described above. Then, the glucose concentration can be calculated based on a sampling current obtained by periodically sampling the electric current from the continuously acquired response current values.
The measuring apparatus, which is provided to continuously measure the test substance contained in the sample, for example, the glucose concentration or the like as described above, is used in many cases for the way of use of the so-called continuous monitoring (measurement) in which the glucose concentration is measured in succession over a somewhat long period of time. The continuous monitoring as described above has the following advantage. That is, the glucose concentration can be measured automatically and continuously in succession, for example, even when an examinee (user) is asleep. It is possible to always monitor the blood sugar level (blood glucose level) of the examinee.
Conventionally, a driving source, which is provided to drive such a glucose continuous monitoring apparatus, uses the electric power of a primary battery (so-called dry battery or the like) in many cases (see, for example, Patent Document 1). It is a matter of course that the measuring apparatus cannot be driven when the electric power energy of the primary battery is discharged and exhausted. Therefore, it is necessary that the primary battery should be exchanged with a new primary battery.